I'm taking a CNC class at FCCJ this term; this is my first project: some
CNC machined, stepped, chamfered injector bungs.
I've got a tunnel ram lower intake on the way that I'd like to convert to EFI
for my S2 motor. I bought injector bungs when I did my first conversion
(pictures and text here).
They're basically just cylinders machined for the injector o-ring to slide
into and seal; they slide in until the injector body hits the bung.
If you look at a factory intake though, there is a step for the o-ring to seat on so that it holds the injector from pushing on through. I wanted bungs with this feature so I thought it'd be a good first project for my class.
I'm using a program called MasterCam to draw the parts and generate the NC files for a Haas mill. The part "drawing" for these consisted of two circles...not very complex. Then I defined 5 machining operations (center drill, drill ID, ball mill stepped upper ID, chamfer, and mill OD). I repeated these on 1.5" centers for 6 bungs from one piece of stock.
These are pictures of the verification process underway in Mastercam; checking
to see that the parts will machine properly.
And here's the final project: start to finish the whole thing took about 3
hours including cutting the rough stock from 1" plate aluminum. I owe FCCJ
instructor Tom Litteral a bunch of thanks for letting me hack things up
when I've only been in the class three weeks!
I'll have to cut these from the plate stock in order to use them; the length
isn't critical since they have to be welded into the intake runners and
cleaned up anyway. I think I'll define a finish pass the next set I do so
they'll have a better outside finish.
